A valley (sag) vertical curve is designed for headlight sight distance (HSD) at night driving. When L > SSD, length L is:
Choose the correct answer
Same formula as summit curve
L = N x S^2 / (2h + 2S tan(alpha)), where h = headlight height, alpha = beam spread
L = N x S only
L = S^2 / N
Correct Answer
B. L = N x S^2 / (2h + 2S tan(alpha)), where h = headlight height, alpha = beam spread
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Valley curve (HSD, L > S): L = N x S^2 / (2h + 2S x tan(beta)), where h = headlight height (0.75 m), beta = upward beam divergence (1 deg = 0.0175 rad), S = HSD. For IRC: L = N x S^2 / (1.5 + 0.035S).
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